1. Field of the Invention
The field of the invention is swashplate type hydraulic devices applicable to hydraulic pump and motor and more particularly is such devices as comprising a cylinder block, a plurality of plungers arranged annularly around the axis of the block and slidably fitted therein, a shoe member disposed at an angle to the block axis for synchronous rotation with the block, and connecting rods each of which is connected at opposite ends to the shoe member and associated plunger via ball joints, at least one of the joints comprising a spherical socket of a major arc longitudinal section formed in the plunger or shoe member, and a ball formed at one end of the rod and fitted in the socket for swing motion of the rod around the ball.
2. Description of the Prior Art
As conventional hydraulic devices of the mentioned type there are known one in which the ball is formed with an annular chamferred portion which is coaxial with the rod and has a diameter slightly larger than the socket inlet and the ball is fitted in the socket by press-fitting the chamferred portion to the socket inlet (see Japanese Patent Publication Kokai No. 62-218664, for example), and one wherein the socket inlet is previously formed of a diameter substantially equal to that of the ball and after inserting the ball into the socket, the inlet is caulked so as to have a reduced diameter (see Japanese Patent Publication Kokoku No. 55-14272).
In the former case, the socket and ball can be subjected to surface hardening treatment such as by GNS or Sulphurizing prior to their fitting. However, their disassembly is prevented only by the press-fitting of the ball into the socket inlet, so that the strength against disassembly is relatively low. On the other hand, in the latter case, the socket and ball cannot be subjected to surface hardening treatment prior to their fitting operation and hence a joint structure obtained thereby will be inferior in anti-friction property.